There is a variety of harlequin called purple harlequin. As far as I'm aware it is just a colour morph of the ordinary harlequin so perhaps the golden headed purple one is yet another variety. All of them are
Trigonostigma heteromorpha. See notes at the bottom of the page in the link. They would be fine in your tank.
My local MA has the yellow variety of honey gourami and the red ones. Very few shops stock the natural coloured ones as in the photo in the profile on here. I failed to find any which is why I have yellow ones. With both natural and yellow colours, females tend to have a darker stripe running from nose to tail even if it is very faint and broken. A fish without the stripe is likely to be male, but some females don't have it and can be confused with males. But if the fish does have a stripe, it's female. Honey gouramis can be kept as 1m 1f as males aren't as aggressive towards females as some other gourami species.
If you could find one of the dwarf types of cory it would leave you more room for other fish. Look for Corydoras pymaeus (pygmy cory, swims more at mid level that other cories) C. habrosus (salt and pepper cory, not to be confused with the larger peppered cory) and C. hastatus (no common name as far as I'm aware). Google pics so you know what to look for.
Galaxy rasboras are now called celestial pearl danio. MA used to call them firework rasboras, they may still use that name. Be prepared for a shop to use any of those 3 names when you look for them.
I had some of these shortly after they were discovered. They were quite shy fish and you may find they hide in a tank with more boistrous fish like the lemon tetras. I would be inclined to get either galaxys or lemons rather than both. That would give you a bit more space to fit something else down the line. I'm always seeing fish and wishing I could fit them in my tanks