There are some rasboras that are similar in looks to white clouds. I had red tailed rasboras (rasbora petensis) that were very nice, good schoolers, but tropical temp. As adults your pearl shouldn't try to eat them. Gourami mouths are small compared to their body size. I've never had a pearl try to eat any fish, but maybe baby guppy size fry? I'm doubtful...
I'm a rabora fan (can you tell?) so maybe harliquin or espei instead. Taller bodied than petensis, all are pretty, & fairly good schoolers. Say 10 or 12 of any 1 species.
What are the dimensions of you 45g? 4ft? A 3ft breeder tank? Or a very tall 30 inch tank?
What about some bottom fish? They are my favs. Little loaches? Corydoras?