I've used a couple diff sets of niods.
The best for the price are the cheap ones you see on ebay. I used them on a couple cars. Right now I have NOS noids just because they came in the super powershot kit.
Edelbrock makes a nice set of them to but as usual u will pay for the edelbrock ,NOS ,NX or other name brand stickers.
try a search on ebay 4 nitrous solenoids.
for 100 shot anything should work as long as they work 100%
Be safe buying used stuff. Had a buddy do that and when he fired his system for the first time the fuel noid didn't fire or closed to soon and took care of his engine.
Buying used plates and bottles are one thing but i'd stay clear of used noids. just get some cheapo ones if $ is a problem or buy 1 at a time of name brand.