I believe they offer wider fittings in some lasts/sizes, as well as some of the lasts being more generous in fit than others. Might be best to email Rezso for specific information, as he knows the lasts best/has them on hand.
Firstly, something about that repair job puts me off. I can't say I favor half soles at the best of times but his treatment is less than stellar. Lear, possibly edge kote? https://www.tandyleatherfactory.com.au/en-aud/search/searchresults/2225-122.aspx
Some Herringbone cashmere knits up on Greys outlet
Alrighty. The shaft of the tree is fixed in place by two press fit pins, one at either end. This makes dis-assembly problematic, but not impossible. If you'd still like to go ahead, I suggest you centre punch them, then drill through them. This should allow you to remove the shaft from the tree, exposing the internal spring. Then just match this spring to something reasonably similar at your local hardware store, they shouldn't mind you opening a few packets to make...