Help on locating part for Orion 80mm short tube

I have an old short tube that I am missing the end piece that holds the 1.25" eyepiece (see attached image.) I see similar parts online but not sure if there would be a thread match where it screws on to the tube. 

Orion support won't help because I'm not the original owner and can't tell them the date / purchaser; I got it used years ago.

Can you help me find this part or a substitute?

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I know this is an old post, but what you are looking for is a 90 degree diagonal. Available from many sources, Celestron's is adequate. $30 used.