wow...so its just a cap..i just put back on? i dont think i have any of those place you named other then a mazda dealer... i have kragen and napa auto parts...

You might be able to get away with not using the pintle caps though I don't recommend it. These two companies service injectors and can hook you up with pintle caps. They just pull right off, so you can install new ones yourself. Though i do recommend having used injectors serviced, you never know how well they are performing if you don't. Replacement of orings and pintle caps is standard with all services from these companies.
http://www.witchhunter.com/
http://www.cruzinperformance.com/

Cruzin turned 4 dirty-ass 460cc Rx7s into brand-new injectors, complete with new o-rings and pintle caps and flow numbers for each one. Best $71 shipped I ever spent.