Correct packing ring for tender pump?

[doublereefed]

The packing ring on this tender hand pump has disintegrated. The pump body is quite thin walled, so I don't think it was an o-ring. I'm not having any luck on McMaster-Carr finding square section rings. Can anyone point me in right direction? Thanks!

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[Builder01]

Graphite string that you can get at the hardware store will work, or, even the teflon type packing string. It will take on whatever shape the packing nut will compress it into. I use the teflon type of packing string on both my hand pump and axle pump.

David