Choices, choices...I would be straight on ebay. I dont recommend
analog storage, they tentd to be difficult to keep working.
Some of the old Tektronix just work, although the power supply
capacitors may fail as in any device.
Tektronix 7000 Y amp switches can be delicate when old and the
mainframe socket for the plug-in.
Telequipment used to be plentiful and cheap.
Some of the Advance (Gould) can be cheap and cheerful.
Do you want collectors age scope too. to go with the age of the
computer, old Tek 500 series.
For computer repair I would also want a logic analyser, you can get a
combination scope/logic analyser these days
although the idea is not new HP1630 logic analyser series started the
trend and dont cost too much second hand.
If you wish to verge on the older scope I may have manuals to suit
http://www.collection.archivist.info/searchv13.php?searchstr=oscilloscope
Dave Caroline