My wife is a fabric artist that has settled in a niche of working withwool fleeces, processing, spinning and knitting. I do the dyeing for her and in the beginning I certainly, inadvertently, have had the experience of mishandling the wool and beginning the felting processing!
Gustin Vintage Heavyweight Sweatshirt - Natural Rainbow Nep - $119 Rugged 14oz cotton that gets better with every wear. 
Grant Stone Diesel Boot Dark Olive Chromexcel - #395 Goodyear welted, Horween Chromexcel, classic good looks. 
Iron and Resin - Buffalo Shirt - $119 Classic, yet modern. 6.5oz yarn dyed cotton flannel with a warm micro polar fleece lining.
I use Tandy Leather for my buckles and conchos. They do online but not certain if they ship to Europe but worth a try.
Interesting. Are you making a hat band? I have bought a child’s belt for a hat before. Got it at winners/marshals pretty cheap. You can probably go for a send hand store as well.
That’s the spirit!!
I have read stories by some folks who had luck with some felt shavings from inside the crown combined with various adhesives. Attempting to kind of refelt the area. Possibly @belfastboy may have some suggestions. Or... the solar fan thing Fruno suggested might be the bee’s knees.
I have had success with moth nibbles and weakened areas of felts. First step is using a sharp Xacto knife scrape felt from inside the crown or underside of brim if you can't access the crown. Then if the spot is very weak or even a hole clean through I glue in a 'boot' to cover the weak spot from the back side. I have a bunch of brim cuttings (I rarely throw things out cuz you never know!). Then using a light spray adhesive that I do not spray directly on the hat as it is not controllable. Instead I spray it on a piece of cardboard (don't do it anywhere near your wife's new IPad as there is overspray) enough so it pools. Then with a toothpick I dab the still wet adhesive onto the weakened area very sparingly. Then the magic of gently applying some of the scraped felt into the area to be repaired. This takes multiple applications....making sure each one is a light layer. If you use too much adhesive it will build up and give you a hardened spot so the art is using a light amount of the glue and lots of the felt. Tamp the felt and you will see that some adhers and the rest stays loose. Take away the loose, apply more glue, then more felt scrapings. It can take a few hours and many multiples of layers. On a light felt the repaired area will show some, the lighter the felt the more it will show....the darker the felt the easier it is to hide the repaired area.
