There is a manufacturer correlation but, in many cases some "universal poppets" have been developed and in a lot of cases it comes down to whether the poppet is short or tall, skinny or fat.
Foxx Equipment has been excellent in stocking a variety of odd poppets at a decent price. They have a website but, you really need to order the catalog to get the pricing. They have a "version" of their catalog in an on-line pdf minus pricing.
They are wholesale but, I don't think they verify.