Sodium metasilicate pentahydrate and Photoresist Universal Developer Crystals same chemical?
Even simple Sodium Hydroxide will do fine, but like PerOxide etching it's taken a back seat, because it's more sensitive to correct dosing to get the right balance between effective and not too aggressive (on the product and/or your hands).

Yes you can make MetaSilicates yourself, yes you can order them. Ordering them will be much more pure.

As for the whole pentahydrate thing, as you should know if you're strong in Chemistry, is just an indication of the amount of water molecules the thing hangs off itself. If you have dry "Sodium MetaSilicate" it'll be a fine-ish powder. If you then leave it open long enough in a normal household you will eventually get clumps of PentaHydrate, because it absorbs water to go to its preferred state of with water molecules.

The only difference between them is the weight of the powder per amount of active ions, so find the right mixing guide for the stuff you order, or you'll be off by quite some. (5 water molecules are quite noticeable in weight against a simple MetaSilicate)