Since no-one has responded, I'll take a shot at this. Not seeing a manufacturers mark on this, you are left with several options: 1) determine what type of vent cap it is. Does it have a hinged lid, curled edge lid, etc. 2) Remove the lid and take it to a RV supply store to see if they cam match it up with a non OEM replacement, which should not be difficult. Replacement lid costs seem to run from about $12 to $25 depending on style and color, with smoke being more expensive. 3) Final option would be to replace entire unit with something equal to, or better than what you have, made a powered fan intake / exhaust vent, although this can be more than you want to spend, or need. Just some ideas and hope it helps. Also, there is a FR rep online now, Wildcat Steve, who may be able to help as he should've the most knowledge and access to older model data.