Try devol for lowering links.
http://www.devolracing.com/
You could go a cheaper route than either you suggested.
You can cut the seat foam down and recover the seat - will gain you an inch or inch and a half.
You can also cut the subframe to lower the seat height. This can be done by actually cutting piece out of the subframe and rewelding it together, or by simply elongating the bolt holes and sliding it down lower. Ricky Carmichael cuts the seat and the subframe and also raises the footpegs to accomodate his short legs.
I'd guess you could lower the seat a total of 2 inches or so - maybe even 2 and a half - and it would basically cost you nothing. Plus, both of those will not affect the handling or suspension in any way.
Yes, you can modify the suspension to make the bike sit lower. However, you will lose some suspension travel and presumably ground clearance.
I don't think the problem will seem as bad to you after you ride for awhile. I'm an inch shorter than you and manage just fine - although my subframe does appear that it may have been cut a 1/2 inch or so.
I have a cut seat that I am about to try out, but I rode/raced all last year without it. I find the height of the bike is mostly a problem in woods riding and on starts. It doesn't really bother me much in the actual race.
I would guess that the springs on the 250 are probably about right for your weight . . .