any symetrical tandem with flat bench seats will work if you want to paddle it from the bow seat  - the 16' royalex penobscot, if that is what you have, is one of the better choices - at 58#, not too heavy to portage  - if you've got a poly version at 75# plus, I can see why you want to go lighter.  Ranger uses his 16' Rx Penobscot when he solos.
A Souris River Quetico 16 (not sure if symetrical, but I think so) is 42# in Kevlar - if your anywhere near Ely, many of the BW outfitters use them, and most will sell used - otherwise, not easy to come by in the rest of the country.

  Hard to get much lighter - my Bell Northstar is 16 1/2' and weighs 39#, but not symetrical so can't really be paddled from bow seat reversed very well (need a kneeling thwart) - you likely want to go to an ultralight vs regular kevlar to get the lighter canoe.

personally, I'd stick with a 15 footer - maybe a Wenonah Prospector in ultralight layup - 38# and $2500 - but I'd never solo a tandem unless I had to so that's speculative.
The Bell Morningstar seems to have a lot of fans as a solo - might find one used.



if you are preferring a used boat, I'd just keep checking Craig'slist for your area and grab the first reasonable candidate you come across

another source is Paddling.net classifides - and thier canoe buyer's guide will give you specs on lots of canoes, and there are also reviews for most of them.

some people do paddle solo in a tandem using the stern seat, piling all thier gear up towards the bow to trim the boat - don't need a symetrical canoe that way