For about a grand Canadian CMSNL has the correct NOS CB450 K1 parts in stock if your willing to spend to make it correct. That is actually a decent price, as an EBay seller wanted $1200.00 Canadian for a NOS speedo for the 1966 CL77 I am restoring presently. I paid a Dutch company about $550 Canadian to restore my 1972 CB350F gauges earlier this year and a US company did my CL77 speedo without replacing the gauge face, since it was NLA, so just a rebuild of the interior for close to $600.00 Canadian all in.
If your doing a frame up it will cost you to do it correctly, yet that bike has many original parts, so it all depends on how much your willing to spend. Chroming is another option, if you cannot find replacement chrome parts. I can recommend a shop in the GTA or Cambridge that does good work, if there isn't a Northern Ontario option.