At least I think that's what it's called ! I need help in getting
one.

Elderly drains (cca 70 years) which have a 90 deg bend at the end of
the house alongside the road heading off to my septic tank. A broken
join a metre downstream of the bend has had to be dealt with, and as
there is no surface access at this point I was intending to replace
the bend with plastic and put in a rodding eye. However a passing
drain man (just happened to be going in next door to sort out their
drains (!) , and kindly showing professional interest) has suggested
there would be less work in putting in a plastic inspection chamber.

Can someone tell me please what I should be asking for and how it
should be seated above the access cover in the existing 90 deg bend.

Thanks

Rob