If you want an older version of Cubase, you’ll have to do some internet/ebay searching and be patient for one to come up, or ask here if someone wants to sell you an old one, as I’m pretty sure Steinberg is not going to sell you anything but current versions.
I don’t know if your Cubase version is a candidate for a license transfer to their new eLicenser dongle so you can keep using it, another user ‘thought’ that was the case, but I’d get an official answer. I do know Cubase VST 5/32 is able to be transferred, as I read something to that affect here in an official Steinberg sticky.
You obviously don’t need full flagship programs, so if you do buy any new versions, get the cheaper lite one’s, as it’ll have less features you won’t use anyway. Though it’ll still looks like the Starship Enterprise 
If you can find a used copy (mine isn’t for sale) Cubase VST 5/32, it’ll look like your version AND you can use it on at least a somewhat newer machine…besides the eLicenser thing.