HP CLJ 2700 / 3000 / 3600 / 3800 / CP3505 Multipurpose Tray
Like most HP/Canon printers these machines have a fold-down multipurpose tray at the front typically used for feeding letterhead and / or envelopes. (Check the user manual to see which types are acceptable). The tray is a fairly flimsy plastic assembly so the parts do get broken.
The tray has three main parts - the fold down flap at the front of the printer with the Logo and printer name on it is RC1-6690. Its quite robust so it should be unlikely to break. RC1-6690 is no longer supplied by HP, the replacement is RL1-1097-000CN. Other parts are not so robust.
The main part of the tray is the RM1-2711. This is held at the inner end by lugs which go into the printer body on either side under the paper-pick roller cams on either side. The tray is spring loaded by two RC1-6383 springs and held by two Link Hinges.
The RM1-2711 looks like this. The Link hinge on the left is RC1-6831 and on the right is RC1-6382.
The RM1-2711 holds the adjustable paper guides but it is not long enough to hold most paper. To extend it there are two components: RC1-6450 and RC1-6451 (The part numbers are stamped on them). These are sold together as RM1-2710
These parts are available here.