I had a Thunder Tiger clip that might be like yours, a spring loaded scissor. Well the plastic broke to pieces within a month and I used an old wood clothespin to reconstruct it it's the best one I ever had. When it got old, lateral slipping became a problem so I glued a pair of aluminum plates to stop it sliding back and forth and it seems to be lasting forever. And the metal electrodes are soft so you can adapt it to all different engines. Use heavy copper lamp cord or speaker wire, keep it as short as is convenient, but if all connections are soldered even 6' works fine. Remember that glow element really draws a lot of current, like 3-4 amps. Most people prefer disposable D alkalines, 2 or 4 in parallel. I don't seem to get as good of a life out of them as those same "most people" but maybe it's because they don't solder or use crappy wire. Or both. That's a great way to get a whole season out of a battery pack Lol.
Just a side note; that current draw makes a 1300mah NiCd like my stunt engine lighters work for about 20 minutes from a full charge. I switched all of my replaceable Dubro clip-ons with sub-C 4000mah Nimh batteries. If I were to make a new pack for my 1/2A fleet I would use Nimh because I prefer the voltage drop off curve over the steady decline of the Alkalines. The 4000mah Nimh will keep it bright hot for well over an hour and then fall off rapidly. And unlike NiCds you can top them off any time as long as your charger knows when to cut off. A dumb charger is a bad idea.
Rusty
EDIT: John, I may have a Sullivan scissor clip. It's old and should be rewired, would you like me to mail it to you?