Welcome to AQ superchevy
Java and Riccia are cheap enough at good LFSes. Riccia is not a moss btw. Christmas might be a tad pricier. Try Nature Aquarium(opposite Thomson Medical Centre), I know they have all the stuff you want there.
For the bed, I assume you're talking about the foreground? Glossostigma elatinoides come to mind. Moss can be tied onto various flat stones and placed side by side to simulate a carpet, Riccia can be done this way too. Or, simply tie them to wire meshes and place them in the foreground.
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