Some years ago, we bought a group of old nib blocks from a long-established pen repair service in England. Most were tool steel in various shapes, but a couple were made of acrylic. Though they had some superficial scuffing and scratches from decades of hard use, they were still as good as ever, which inspired us to use the same material for a new run of nib blocks, enabling them to be priced at a level affordable for every pen hobbyist.
In fact, while there are some applications where steel has no substitute -- hammering, for example, and heavy-duty burnishing for displacement and hardening of metal -- acrylic has the advantage of having just a slight degree of "give", just enough to allow one to use pressure to apply bending force, as when one wants to straighten by counter-bending. Metal doesn't allow this, which is why a strip of thin paper is sometimes laid over a metal block to provide that "give" that the bare block lacks.
The blocks are now listed in our website catalog here, at $25 each. They are also available on eBay. We'll be bringing some along to the next few pen shows we attend, which will be Madrid and Los Angeles.