There's no equivalent I know of in the bass uke world to a dolphin for a beginner to try out.
Without a budget of $400+, you're not in the market.
That might be over the top for many uke players, but it's the starting point for uke bass.
If your buddy has had a uke bass in his hands and expressed the desire for one, great.
If not, it's an expensive present that you might want to make sure can be exchanged or returned.
Something thing to keep in mind is that unless you're alone in a quiet room, there's no such thing as an "acoustic" uke bass.
To be heard, they must be played through an amplifier.
In a group setting, you can be sitting next to one and you won't hear it unplugged. So part of the price is the pickup and electronics.
If you buy used, it's important to critically check the sound through an amp, as they use under-saddle pickups that can have technical issues with even volume from string to string.
Another difference is the fat, soft, stretchy plastic strings are nothing like bass guitar strings.
Most old bass players (like me) take to them, but they're quite an adjustment in playing technique.
Kala was first to market and so is the standard.
I bought a spruce acoustic and a solidbody as soon as they became available a couple years back.
An alternative is Ohana's new uke bass.
I've played one, it's the same size and sells for a little less.
Mim, HMS, et al should be able to get Ohanas as well as Kalas, so you'd know there was a reputable dealer backing it.
One idea might be a gift card from a dealer, then the old rocker could get whatever he wanted rather than have a bass uke under the tree Christmas morning.
For $500, instead of a Chinese factory bass, there's a whole world of classy ukes.
There are thousands of posts on Kala u-basses and their clones from the perspective of bass players here:
http://www.talkbass.com/forum/f8/kala-ubass-megathread-part-6-a-964655/index47.html