Hi Andy
Try contacting Baglux for a tank cover. They don't list the XBR in their catalogue but they might be able to sort something out for you. I've heard of them doing specials for people, it won't be cheap, mind. Let's know if you get anywhere with it.
I've never done an XBR seat cover but mine's starting to split too. From past experience, pattern seat covers are a bit hit-and-miss, particularly if there's any kind of shaping to the foam. If we use them at work we tend to pass them over to a bloke in the local chopper club who fits them for us. They usually require a bit of modification - stitching etc, and you need a fairly hefty stapler to get into the plastic base.
I'm with you on the membership thing. I'm fairly peripheral as club members go, I've not made it to any meets yet, but I've got a lot out out of the website over the past few years and I wouldn't object to sticking my hand in my pocket if subs were required.
Cheers,
Dave B