You could pay an inflated price on eBay or you can buy the Mod Classic 45s Box Set from a retailer online.
Thanks to Mark Colley for the tip off, pointing out that What Records is selling the boys for £39.99 right now. That’s a lot cheaper than Piccadilly Records (which is odd), as well as a lot cheaper than the current ones on eBay, which are going for £60 and upwards.
No idea how much stock they have and I don’t personally know anything about the retailer. But if you are interested, check it out here.
You can read up on the box set here too.