Welcome!

Many kiltshops in Scotland have ex rental and/or 2nd hand kilts for sale.
Must be lucky to find a Saltire though (Royal Stewart, Black Watch, Cameron of Erracht and some others are pretty easy to find).
A kiltshop in Drumnadrochit (near Urquart Castle) had a huge amount of 2nd hand kilts in stock....maybe give 'em a call?

I don't know the name of the store, but you can send a PM to Rab Gordon...he lives there...he will know.