Spunding Valve - Pressure relief valve part question

So I built my spunding valve the other day but accidently lost the little ball that sits in the pressure relief valve (I used this Mcmaster Part number 48935K25) What is the ball made of? Is it stainless steel? I seem to have lost mine on the (fairly dirty and uneven) garage floor somewhere and before I get on hands and knees trying to find it I wanted to see if it would be easily replaceable? Or maybe it is magnetic and I can use one of those finder wands to try to find it. If nothing else, I guess I just buy another relief valve and have backup parts, but I really dont want to put another mcmaster order in, those tend to get dangerous on the wallet.

You can see how dirty my garage is by my lack of hope of finding it.

Any help is appreciated.

Hopefully you've found it by now, but yet, they're stainless steel

Never found it, bought a second (and then a third showed up from my dad who is a chemical engineer and works in a lab).

Make sure you put something before this pressure relief valve to completely shut off pressure. This valve will not hold 0 psi. It always relieves something.