Since it's blunt now, you might just as well have a go at it.
3M makes a whole series of fine automotive finishing sandpapers. I go as far as their 1500 grit.
Figure out what the bevel angle is. Failing that, paint the bevel with black felt marker to see how effective you are.
I suggest dead chainsaw files as mandrels to do the gross serrations.
600, 800, 1000 & 1500, a sheet of each, won't break the bank.
I have one of these, albeit the fine edge version, and I'd go along with Robson Valley's suggestions; accept the loss of the fine serrations and if you don't have any dead chainsaw files to hand, fold fine emery paper round a suitably sized rod (knitting needle, perhaps) for the large ones.
Avoid sharpeners aimed at blades that have a bevel on both sides. Your Ridge will be flat on the inside of the blade. The Tri-Ceps looks like it should be fine.
It's really only the tips of the serrations that blunt in general use. As this knife is a fairly cheap user, I wouldn't worry too much about getting right into the curves as I doubt they're blunt.
As suggested, some wet and dry paper on a flat surface. It'll pick up the straight edge and sharpen the tips of the serrations.
As for replacements, you'll need to tell us more about use, as in locking or not etc. There are many knives that may suit, the Chinese (Sanrenmu, Ganzo, Navy) offerings being very good value for money.
If I'm honest, that knife looks uncomfortable in use, and is a locker so unsuitable for everyday pocket carry. If you can carry a locking knife as a daily user, then I may have something far more capable for you. Been clearing the cupboard, turned up a few.