eBay and Craigslist finds

Kelvin Watching a stem that the seller reckons has a 25.8 is aint a standard size is it?

If i get it would I be better shimming a 25.4 or seeing if I could squeeze a 26m in? or should I just buy another stem...

Wiki says:

The ISO standard for the clamping area of a handlebar is 25.4 mm (1"), which is used on the majority of mountain bikes and many Japanese-made road handlebars. However, the Italian unofficial standard is 26.0 mm, which is the most common clamp size for road bars. There are also intermediate sizes such as 25.8 mm to try and achieve compatibility with either an ISO or Italian stem, and the old Cinelli-specific size of 26.4 mm.

Which implies you should be able to squeeze a 26mm into the stem....