Re-tightening my seat post, I found that the keyed (?) nut was turning, and has now stripped it's home. Think a quick-release will work in it's place? I won't know until I get home. I hope the seat doesn't drop on me half way....
So much for Vitus 888. (Seems that Moto should use hardened steel on that spot.)
I have seen quick-release type seat-post binders, I guess designed for urban areas where removing the saddle is a way to deter bike thieves.
My biking buddy and I were out on a ride when her seatpost bolt broke. Get some duct tape, and duct-tape your seat-post to the frame. When you think you've used enough duct-tape, you should probably use some more. That patch-work solution held for us for over 20 miles until we could make it to the nearest bike shop and get a real replacement.
The quick release seatpost binder is a very good option and should be a low cost replacement. As mentioned, useful in urban areas as a theft deterent and useful for riders who wish to change their saddle height in mid-ride.
My wife's solo bike has one. The stoker seat post on our tandem has one. Hmmmm, I'm seeing a trend here.
you might be able to find one of the "other" type of seat binders although they are a bit hard to find now. there are even campagnolo ones. (i used to see them on cinelli steel frames if i remember correctly) instead of a key they have splines that wedge themselves in all the way around. there is also an allen key socket on the other side so you can hold it in place (with a second allen key) while you tighten/loosen.. it is very important to grease the threads and the inside of the hole in the frame where the bolt part moves because the lug angles as you tighten it. often it is not a very perfect fit.
or you could just get a keyed type one like you have and just use another allen key on the other side to stop it moving. (i assume the one you have now has no allen key socket on the other side, most of them do now)