Reddit mentions of iExcell 100 Pcs M4 x 8mm/10mm/12mm/14mm/16 mm Stainless Steel 304 Hex Socket Flat Head Cap Screws Bolts Kit

I am on my third psu now. Yes, that is the correct fuse and it supposed to be slow blow. It's an exact replacement.

Bad news is, I'm almost certain It's not just the fuse that is blown. The mk3's psu's are well known to fail, and while some people say that there are just bad apples, I think the psu can't handle the higher draw when printing higher temp materials. If you were to open up your psu, I'm almost certain you would find the permanent on board fuse soldered to the board to be blown as well, and possibly also one of the components busted and burnt where it failed. Prusa will replace the psu under warranty, but in my case it just happened a second time. Same thing.

So here is what I would do if I were you. Go on Amazon and buy this. Not only is this psu way more reliable than the cheap Chinese one prusa ships with, it is capable of much more and will not fail you. Well worth the 30 bucks. This is the mount you will need to print to attach it to the printer. This fits perfectly, and uses mostly the screws and nuts from the stock psu except for one kind of screw you need 5 of. I made the upgrade and it is so much better than the stock psu. It has a fan that makes the printer slightly louder and it runs intermittently, but it also gets rid of the ticking from the heated bet and makes everything run a bit smoother. You can either hook up the replacement prusa sends you temporarily in order to print the mount, or you can do what I did and hook the meanwell up next to the printer to print the mount then mount it properly. Just be careful if you do as there will be exposed terminals that could shock you.

There is a great write up on the prusa forum detailing exactly how to do this and everything you need