I presume you could put nikosil over the steel but you would still have the expansion problems inherent with aluminium pistons and steel bores. They expand at different rates. It would probably be worth looking into if you were keeping the bike for a long time but its around £100 per bore to have it coated at the very least, might be quite expensive.
You could try ringing a local plater or maybe stan stephens, they are in touch with a quality plating firm for all their work no doubt.
That being said you might try looking at a re-bore of the current liner instead of trying to return the bores to factory fresh spec. PJME offer a rebore service at £30 per cylinder, you would have to ring them and ask how much they would need to bore it to get it back to being round again and honed properly. Its possible you could do the stock worn bore with a slight rebore and hone and use the stock pistons but you may be at the upper limit of the maximum piston to bore clearance. If that was the case you would need to rebore to suit oversize pistons instead.
Have a look here :
http://www.pjme.co.uk/acatalog/Cylinder_Re-Boring.html
I and many forum members from 125ccsportsbikes.com have used PJME so i definitely trust their work, i have personally spoken to the owner so i know he knows his apples. Who do everybody from 400GB usually use ?
If you can get your engine sorted back up to high compression as its supposed to be it would be faster too.
on the above, my problem was due to a cheap chinese CDI havving an issue and not cutting the revvs at the red line, i overtook an R1 then realised i was doing about 25k rpm 
then pop hole in the piston.