Can someone recommend some age gap yaoi, preferably early 20s x a mid 30-40 or even early ...

most of naono bohras waork have a big age gap

Cheers

Try reading kokoro (kanda neko)

http://www.mangago.zone/read-manga/mayonaka_no_oyatsu/
http://www.mangago.zone/read-manga/joou_to_shitateya/

http://www.mangago.zone/read-manga/unfather/

http://www.mangago.zone/read-manga/on_doorstep/

http://www.mangago.zone/read-manga/hana_wa_saku_ka/

http://www.mangago.zone/read-manga/how_sweet_is_a_sugar_daddy/