I am struggling to find glazing bars to do my conservatory roof.
Following suggestions I will be using glass and not polycarbonate.

My conservatory came with alumnium extrusions for this. They sealed to the
glass using rubber seals. You can probably get them from loads of places. My
conservatory was supplied by Baltic Pine. They might be willing to send a
few bars (complete with rubber seals) if you ask them. If was doing it, I'd
try to get them to supply the rafter mouldings and seals as well. The glass
was laid onto rubber seals on the rafter mouldings, with the capping bars
also sealing with rubber. The system worked like a dream.

# = rubber seal.

_______
/_______\ - capping bar
#/ +---+ \#
------------+ +-----------
SEALED UNIT | | SEALED UNIT
------------+ +-----------
+##+ +##+
| | - wooden rafter moulding
+---------+
| |
| |
| | - rafter beam
| |
| |
| |
+---------+

Christian.