This peg is ready to fill your .25" (6.35mm) holes. I use it to mount light gear such as tweezers and eye protection. It's a super snug fit and will not fall out unless your holes are oversized from wear and tear.
This is a "remix" only in the sense that I got the idea for this peg and its general shape from @royimous' "Peg for Pegboard". Mine however is an original design.
I printed with an SLA printer, but I suspect this will print fine with supports on FDM.
Formlabs tough resin
Cured 120min @60C