So much for being patient. Sounds like you want that Master finished
today, if not sooner, LOL.
A good way to determine what an item brings at auction is by using the "advanced search" on eBay. Find it, click it, enter keywords you are looking for (sometimes it'll be helpful to also add terms you don't want to come up in your search - under "exclude these words") and then make sure you click "completed listings only" and you'll see all the auctions that have ended in the past 10 days. What they sold -or didn't sell- for.
Here's what an advanced search for "dominator seat" yeilded:
http://search-completed.ebay.com/dominator...pZ1QQsofocusZbsAs far as I know, the only 3 piece cranks to come on the '88 Master where Peregrines, yes.
Best of luck finding the sprocket you want...the Haro team one, anyhow. I think Bob (djbdb) looked for more than a year to find a suitable used one. I would contact him personally for more questions specific to this build. His came out absolutely perfect. He's selling off quite a bit of his collection (everything but his black Master), and he might have some spare parts. You might find it easier and cheaper to find a Peregrine sprocket, which are a good substitute, IMO.
Once again, I'll just suggest that patience is the key. Yeah, it's worth whatever you're willing to pay for it, but when two or more impatient people go head-to-head on an item that they positively have to have -right now- that's when the price a a Dominator breaks 2 or 3 hundred dollars. We all know what happens THEN. Earl and a bunch of the NOS sellers start listing all their Dominator seats with a Buy It Now of $250...ugh.
Just keep in mind -and I'm not suggesting this is you- but those of us who've been around a while have seen many a new guy come through who are looking to rebuild their past. They come in, buy everything they can in a orgasmic burst of nostalgia, and the next month they are unsatisfied/discontented or whatever, only to sell off their "dream bike" for a substantial financial loss.
Good luck. Take your time and savor the process of accumulating the parts you need. Years from now, that search, in itself, will be a fond memory. Dig?