So that you may spend your open neurons elsewhere, I present: rhymes for "penis." I, handily, have a rhyming dictionary. I couldn't find "penis" (this book is so old, I guess it wasn't a word Apollo Editions expected would require a rhyme), but:

Cleanness, meanness, greenness, keenness, leanness, genus, Venus, sereneness, obsceneness, uncleaness

OR, you could cheat:
Obscenest, serenest, routinist, machinist, plenist (WHAT does that word even MEAN??), magazinist

OR, you could alter the pronunciation very slightly:
Beanish, leanish, deanish, cleanish, spleenish, meanish, greenish, keenish, queenish

Never let it be said I do not care about your bandwidth!

Hope you're well,

C