Just buy them from Dan Miller.
I live in England, so looking for local suppliers. The washers at manveer's link have internal diameter 2.125", reckon that's a good few mm wider than m48 so I'll go a size up. Thanks!
Sorry Chebase88, the M number is how you say the size of a bolt in the metric system!
Couldn't find a source of m52 washers that cost less than a pair of .5kg plates listed on eBay, so i went for the latter.
Thanks for the advice!
Thanks, this explains the sudden influx of orders the past few days. Unfortunately I can't economically be of assistance to OP due to the cost of international shipping. For those in the US, details can be found here:
Microplates for Sale