It's not going to be cost-effective to rechrome the exhaust. Cost will be about twice what the pipe costs new because they have to strip off the old plating and repair any damage to the surface before the chroming process; labour is expensive. Unless this is a hard-to-get vintage part, you are probably better off continuing to look around.
Two possible chroming companies.
Automatic Coatings in Scarborough.
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Cambridge Custom Chrome Ltd.
10 Clemens Ave, CAMBRIDGE, Ontario
Telephone: (519) 658-6681
You might want to consider ceramic coating instead. It is cheaper and more durable. It also can come in a chrome-like finish called ChromeX.
Possible ceramic coatings firm
HTC High Tech Coatings
888-225-8648.
2256 County Rd 31, Ruscom ON N0R 1R0.