Will the supply of spare Garand parts ever dry out?  If they do, would there be any alternative?

What kind of spare parts should one have on hand for their Garand?

Compared to M14 parts, the supply should be good for some time. However, I am collecting odds and ends such as a spare trigger group, bolt parts, bullet guides and all springs and pins. Gas cylinders are a necessity as are oprods. Orion 7 is a good source for parts. A spare rifle is best................

Don't forget Op rods.

Op rod and gas cylinders are the heart of he Garand.

The supply of parts, particularly unused parts IS drying up.

It's getting harder to find items like hammers, triggers, bolts, op rods, and sights in really good shape.
A good amount of what you're seeing is worn, refinished parts, and non-GI "Replica" parts made from cheap castings.

Of course, the supply of like new stocks, barrels, and gas cylinders is more or less gone.

The supply of ANY gun's spare parts is finite, and sooner or later dries up.

With the number of CMP and import M1's, people are buying parts and the supply is dwindling.

If you're smart, you'll buy as new a set of spares of EVERYTHING as you can find.

Years ago, when I bought my M1 from the DCM, they carried a good number of brand new in the wrap spare parts, and I bought at least one of everything they had available.

THAT was a circus.
The DCM ordered the parts to be shipped from whatever arsenal happened to have the part.
USP refused to just leave the shipments at the door, so I'd have to drive about 20 miles to the UPS depot to pick it up.

For about a month, every day I'd have several packages in my mail box, and a notice from UPS.
I'd drive the 20 miles only to find a single envelope with a single small pin or other part in it.
Next day, another notice and another part.

The up side is, I have a small supply of brand new USGI M1 parts.