I'm fascinated by the Risa.
They don't seem to be very availble in the US though.
DeSilva is the only place I can find.
Shazzbot: Darn, there's been about 2-3 on UU Marketplace within the past 6 weeks or so. They usually sell fairly quickly. (one recent seller, as I recall, didn;t answer his PM's and it upset some pot'l buyers). I played mine today--a RISA stick soprano--and it's lovely, just lovely. Entire package is (I'm measuring it right now) 18 inches by 3.25 inches wide by 1 inch thick (you can carry it in a messenger back or backpack easily), and I just tossed mine on a scale and it's (with strap) 15.44 ounces. Unlike a Flea or other uke, this one is nearly indestructible. You could step on it with workboots and it'd be fine. If they make you check it (unlikely, as they won;t even know you have it--it'll be neatly in your bag), even the baggage handlers can't smash it. It comes with a perfect fit custom padded gig bag, and the uke strap serves also as the gig bag strap--how neat is that@!
I was having issues, as you might see on the thread, with tuning, but I have it sorted out--it was me, not the uke. And I have the older friction tuners (now they are geared) and I have no more problem with them than any other friction tuners. And it stays in tune well. German made. You would put out a WTB in the Marketplace and see what turns up, don't know when you're going to Costa Rica but keep eye out, and as you're going for two full weeks (plus other trips on the future), it's a reasonable investment (I think the soprano is about $275 new--there's some sellers on eBay). Not as rare as you'd think. Bulletproof for travel. And you can even play in the airport as you can hear it, but it's not overpowering for those around you. Then, if you want, get a tiny Fender or Honeytone battery amp and a 3 foot guitar cable. Or, just forget it and be pleased with it as is, acoustic.
No guarantees that you'll be as cute as the girl on that third video from playing one, but it's still cool. lol And, I have little doubt, the sloths will open their eyes and look at you when you pull that RISA out from your backpack and play your ukulele waaay out there in the rain forest. lol