Replacement Battery Source 1990 200 TQ

[Blake Gibb]

Does anyone have a suggestion for a good source for a replacement
battery for my 1990 200. The current battery has the vent cover that
hooks to the vent tube to exhaust bad nasty gases. Most batteries do
not appear to be so equipped for the vent hose. Also, if I hook up
another battery to the front aux post(in engine bay) with jumper
cables will the radio keep current while I remove the old battery. I
don't have the radio code. I know the dealer where my car was
originally sold, would they be able to supply me with the code?
TIA
Blake
1990 200 TQ 187K