Welcome aboard Allan!!
The Ultra frame is the same as a Handi frame, they both have SB2 frames, the only limitation concerning your frame would be when it was made, the 204 Ruger barrels is a high pressure chambering, one of those marked with an * on the accessory barrel list, and can only be fitted to frames made 1999 and later, you can find the year of mfr info in the FAQs and Help sticky along with a lot of other important info including retail stocks available from H&R. Factory accessories are only hard to get if you don't know how or they're out of whatcha want, right now they're out of the Boyd's laminated thumbholes for a while. Brownell's also carries some of their stocks as well as other parts. Be sure to see the link in the FAQs "Let's see some Handis", lots of pics.
Triggers can be worked on by any gunsmith, or you can do your own, DIY trigger job info is in the FAQs also, or when you send the frame in for a barrel and stock, you can ask that it be reduced 3-3½lbs, depending on how heavy it is, they may or may not charge for it, usually if it's over 5lbs, they won't charge, but if it's already under 5lbs, they might charge $15, they have before.
Tim