Have been having issues with fork seals not sealing for very long, inspected the chrome & there are no nicks or rust etc on them

The leg that has the biggest problem definitely has noticeable movement when extended so it looks like the top of the slider is worn

I'm thinking that I'll need top have them bored & bushes fitted but so far I haven't found a 34mm fork that uses bushes that I can use & the coated bushes that can be bought from bearing suppliers are either 32mm or 35mm inside diameter 

Any suggestions of a fork that I've overlooked or somewhere that may be able to help

Your best bet is to try a local engineering firm and get them to bore the legs and machine a bush to fit. The TY250 stantion at 34 mm is a bit of an oddball size. Either that or get the legs honed out to 35mm and the yokes as well and fit 35mm stantions which are widely available. Very common in Pre65 to have the sliders machined to take 35mm stantions. Good luck.