Replacing it with a newer unit shouldn't be a problem.
There are many on the bag. Most new ones are boxes and may be easier to hide.
http://motors.shop.ebay.com/i.html?_nkw=charcoal+canisterSome newer canisters are nearly identical to Mopar canisters of the day which leads me to believe they were probably made by the same company.
GM
http://www.ebay.com/itm/270946231006Nissan
http://www.ebay.com/itm/180855366667Jeep
www.ebay.com/itm/130673142627Old Mopar
www.ebay.com/itm/150631341834All the canisters should be labeled (Purge) (Vent) etc. IT shouldn't be too much of a problem to plum a new one in place of an old one and just cap the unused ports. My 73 uses the same can as my 74 but my 74 has no bowl vent so the port had a cap from the factory.