www.semillas.de has a lot of them - all different types. Based in La Palma but write in German or English (slightly wonky).
Reasonable prices and P&P, fairly quick too. But Roquito/Rocoto/Locoto/Manzano peppers are 100% perennial (but not frost hardy) so are worth sowing anytime up to May - if you can resign yourself you to green peppers this year and a big yield of ripe ones next year. Even smaller plants from a later sowing are even easier to overwinter anyway.
Obviously if you want a third+ season you need to grow them to fruit in pots, but pots buried in a greenhouse border do well. Last year they actually preferred to be outside (being from mountain areas).
Cheers.