You can find the parts in McMaster.com.
92474A026 Female threaded round standoff, zinc-plated brass, 1/8" OD, 1/2" long, 2-56 thread size $2.73
91802A079 Passivated 18-8 stainless steel phillips oval head screws, 2-56 thread, 3/8 long, packs of 100 $4.46
McMaster-Carr's shipping cost to from Georgia to Texas is a bit over $10, via either UPS or USPS.
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I disassembled a harmonica that Bill Romel put together for me. I visited several hardware stores and McMaster-Carr website in order to come up with this formula.
I bought extras. For one chromatic harmonica, we need two of the standoffs and four screws. I will send you two standoffs and six screws if you send me a stamped self-addressed envelope and a ten dollar bill. Find an email link to me by clicking on my name on the left side of the screen, and I'll give you my USPS address.