How much of a height difference do you need? Bearing in mind it is better to have tweeters at or just below ear level rather than above that level.
If you are happy with the nexus range then you could get a 70cm high pair (Currently retailing around £80..)
Would this put them at correct height?
I am assuming you have standard 60cm stands. If so try sticking 10cm of books /newspapers / something on top of what you have, stick speaker on top of that and remeasure height to centre tweeter, compare that to your listening ear-level.
If its better positioned this way you could always flog on your old stands on Gumtree or the like.