Seraph Weapons in Oasis

I have spent some time getting my stock of Seraph crystals as I want to try the Evolution Shield alongside a Blood of Seraph relic. However after visiting the Oasis Seraph store 20+ times there are only ever a total of 4 guns (SMG’s and Assault Riffles) in the Weapons section. is there a trick to get weapons like the evolution, Ahab, Patriot, etc to appear?

The Evolution only drops from Hyperius in UVHM. Ahab and Patriot are from Gee.