It is not uncommon for suppliers not to want to supply replacement parts: it cannibalizes on their sales of the complete products while it is frequently not a profitable business. Moreover, the logistics are very unfavorable. Suppliers usually don't end up making money of of replacement parts. If they do it (unprofitably), it usually is to prevent hurting their reputation. Supplying small quantities of many different parts to many different destinations is expensive. Plus, you usually end up manufacturing many parts that will not be used, because it was hard to determine which ones will break and which ones won't. Because you have to speculate which parts to produce in which quantities, this creates the problem of under- or overstocking parts that need to be stored and collect dust somewhere until the stocks either run out or become obsolete without being used, ever.
Being able to fabricate independently from manufacturers and "on demand" is a completely different scenario. My parents have a large garden parasol (a.k.a. sun screen) with rods that keep the skin up. The fabric of the parasols sown to the little caps that I'm replacing. The rods have end-caps that have worn out over time. The rods now protrude the broken rods and/or the places were it was sown broke the piece.
The broken/replaced parts are the semi-translucent bits alongside the yellow ones.
The parasol picture is from this website:
- Print as many as you need.