For the Officer: =) I don't know if any of these will be what you're looking for, but I wanted to at least give it a try. Personally, I'm thinking the Miamouse for your Xweetok may be your best bet.
The Knum seems to match...well, fair...as is (no painting), is cheap, and has a good number of other colors available. The Nuk costs roughly between 30-40K, but doesn't have a whole lot of color options yet. The Puppyblew just by itself is affordable, but I don't know if it matches well enough for you to spend the NP to paint it brown, especially if you might paint it again later. I put it as an option though because it also has a fairly wide range of color options.
For your Grey Acara:
Let's get the obvious Grey-to-grey matches out of the way first.
I picked these pets because the unpainted ones are cheap, and once they're painted, they match pretty well. (Grey Harris might be a little dark.) I mean, a Grey Faellie looks great as a match, but just the plain Faellie alone...well, let's just say that when I could find one on the Shop Wiz, I took that as a bad sign. I haven't checked the prices of a Grey PPPB lately, but if they're anything like the original PB...
Here's a few color matches in case you decide you want a grey-<i>colored</i> petpet, but not necessarily a grey-<i>themed</i> one.
And finally, some happy brightly colored petpets if you want contrast.
If the Grey Acara's a long way off, TNT may also release some Grey versions of, say, Miamouse or Magaral, that might match better.