(sorry, i might have misinterpreted what you're meaning with oil bungs)
are them what you're looking for?

http://www.enginecoreplugs.co.uk/pro...i-xr3-xr2i-xr2

http://www.burtonpower.com/core-plug...1-8-cv100.html

but you might looking for the threaded block plugs or others...
in such case, if i were you, not being able to re-use the old ones (even with sealer pastes or teflon tape), i'd fetch them to some serious spare-dealers or engine-machining-shop, trying to work something out...
they may be the same used on other engine blocks.

hope being helpful...