Great question, I had a similar situation, where I work we use a lot of Viavi (old Aeroflex brand) test equipment, the accessory kits available through Viavi are Eagle parts, the good news is Eagle still seems to be making parts but as far as I can tell they don't sell through any distributors other than Viavi. I recently smoked a precision 50 ohm load from one of these kits and I wish I could find the direct replacement part but I've noticed the same thing you have.
I'd love to find a source for these traditionally reasonably priced precision components outside of ordering accessory kits through Viavi but I pretty much decided they just don't exist outside of the occasional used listings on flea bay.