The friction slide thingies used on modern windows instead of hinges ought to be well up to the support job. I have a stash of used ones in the "gotta be useful" box. If you fancy trying the idea PM me and a pair are yours for postage costs.
The locking struts in Brians link are effective but, if the ones I saw are the same model, quite hefty.
Eurofit offer a variety of lid stays :- **LINK** including light duty gas struts, smallest is 50 newtons force, about 11 lb.
The ordinary folding desk stay like this :- **LINK** can quite easily be modified to work as an over centre toggle type support as described by Nigel. I did one many years ago which worked OK. Darned if I can remember exactly what I did tho'.
An ordinary drawer slide will do the deed just fine if you ass a sprung clip. In principle its easy to come up with a two position clip which releases if you push the lid beyond its holding position and re-arms ready to support the lid next time as you swing it shut. In practical its probably more works than the job is worth.
Clive