I believe the old Cox Blue Can fuel was 15% nitro and 25% Castor. You would probably save money by modifying one of the readily commercial brews, as opposed to getting it on-line. HazMat fees will eat you alive!

You don't mention what commercial brands are available, but if Powermaster or RedMax is available, you're home free. Just ask the LHS Owner to order you a gallon of the correct blend the next time they re-order for their own supplies. You may be asked to pre-pay, but you're only looking at $20 or so.

If you have to modify one of their blends, get something with 20% Nitro and as much oil (preferably Castor) as possible. Then add SIG Castor oil to bring up the oil content to at least 20% - 22%. Good luck.

I like the Powermaster 15/18 fuel with 8 ounces of castor oil added per gallon for most of my 1/2As.  For Tee Dee engines (all sizes) 25% Nitro is good.  SIG fuels are excellent.

I found some Norvel 35% Nitro at a LHS when I bought my Norvels.  Makes my buddies Golden Bee really scream, but still cant hold with the newer engines.

On 35% Nitro, if he doesn't re-set the piston/rod ball socket joint after every single flying session, that poor little Golden Bee is not long for this world! And it's still probably turning under 20K rpm . . .

Here I am still running my half A's on the same fuel I run in my big stunt engines.  Just done lean them out so much.  Have fun,  DOC Holliday