Frank,
  I'd call TP and ask if they can custom make it for you since their batteries are assembled in the USA( At least I think they are). Worse case put two 3 cell together and solder together and make up an adapter at the balance end only and keep that at the charger so you dont have you carry all that extra wiring. TP is currently running a 30% off sale at the moment Discount code "FREEDOM"

Such Y cables are available, I used them. But it should be installed permanently (and VERY carefully), because it can make short if improperly connected.

https://hobbyking.com/en_us/6s-battery-pack-balance-charge-adapter-lead.html?queryID=639292fa056086057aaf1edc3269ae87&objectID=26353&indexName=hbk_live_magento_en_us_products&___store=en_us
 

 Brent :
They're 45C and 65C packs.
25C is what most of us use.
Thx just the same.

Try China Hobby Line.
https://chinahobbyline.com/index.php?route=product/category&capacit_min=1734&capacit_max=2246&battery_min=6&battery_max=6

If you've ever wanted these(or even a 5S 25 C 2200), please contact Kim Quenette at Thunderpower RC @ 702-228-8883 , select option 1.

 Apparently, they must certify each pack size ($) and it'd would help them determine need.

 I tried.

Try China Hobby Line.
https://chinahobbyline.com/index.php?route=product/category&capacit_min=1734&capacit_max=2246&battery_min=6&battery_max=6

In my search for a 6s 25C 2200 ish mAh i discovered that they are not very practical. I investigated the option of 2 packs of 3S and the option of actual 6S 2200.

The problem with the 3S is that it take two charging stations to charge for a flight so I passed on that idea since there was no weight savings and added complications, in addition to that they all came either just as heavy or heavier than the TP 6S 2800 .

The problem with the 6S 2200 is that they are made for drones and they are 55C and above rating which makes them heavier that the TP 2800. After flight with the TP 2800 my batteries are at 3.85V per cell which is right in the storage charge window so no post flight storage charge was needed, if i was using the 2200 which are heavier I might have to go store charge the battery after I go out flying. This all got me back to why change? Those batteries are not lighter, they are not easier on me the user since I have to worry about storing charge, I do not have to make an additional purchase so there was no reason for me to pursue them.

To me the only option is to use the recommendation from Jim V wait for the packs and run with it but if they go out of business or you need to renew your stash you are in a pickle because you just painted yourself in a corner.

So what are the alternatives? Up the size and KV of the motor go to 2B light props for more efficiency. All of this will work great on 4S and these options are all very practical and readily available.

Frank, I've dealt with Kim from TP before for warranty issues and she was very helpful and responsive. I might be interested in 6S 2200 TP packs. Could you detail your setup (plane size, weight, motor, prop, rpm, line length) that gives you the battery consumption quoted above?

Hi Rick:

Thanks for reaching out to Thunderpower. We need more flyers to do the same.

 Hi Mike : I have a Caprice that flies very nicely with the Hubin system. 4S 2800, Power 15, CC ESC, APC 11 x 5.5 EP. .014 lines 60'.

I'm looking to try an active system . IMO, the battery is the Achille's heal when it comes to using a 5S or 6S in a a Classic (or profile model) if one wants to go with an active system. Weight and size are crucial. Why dump a heavy 5S or 6S 2800 when a smaller mAh will do the job and some?

 Weight, packaging and suitability needs must also be considered when choosing the  ESC, motor and prop.

Currently, there is no readily  and reliably available 5S or 6S 2200 mAH that's 25C. There is a hobby shop in China that claims to have the 2200mAh. But communications with them are at best, murky. I'll stick with TP.

48.7 ounces

The problem with the 3S is that it take two charging stations to charge for a flight so I passed on that idea since there was no weight savings and added complications, in addition to that they all came either just as heavy or heavier than the TP 6S 2800 .

Paralleling boards are not expensive and you can charge several batteries at once. I routinely charge four 4s 1800 at a time on my charger. The boards are generally less than $20. I wouldn't let that be the thing that makes up my mind for my battery selection.