I found this out by coincidence. I hope it works for you too, but I can't guarantee it.

How to download vid from porntrex.com without registration

This works for me on PC with Chrome. First, we need some plugins
1. Add blocker. I use https://chrome.google.com/webstore/detai...phjbkeiagm
2. Video downloader. I use https://chrome.google.com/webstore/detai...jpinpmmpil
3. go to porntrex.com
4. search your vid in the search field on top. The field on the left side doesn't work for me.

Note: Their search engine is crap. It always works in "OR" mode, showing results with any single term you enter.
But you can filter your search results by checking the circles on the left side.

5. go to a video, set the quality on the gear wheel symbol bottom right corner of the vid. It starts to play, you can pause after setting the quality..
6. Use your video downloader to download the file.

Note: 4k files tend to be large. I've got some VR vids with 2-3 GB.

Quick search: over 900 results for "pregnant".
Filtered for VR shows 5 different vids in different resolutions.

If you find that guide helpful, I appreciate the like button, but if you want to thank me with access to your vids collection on Mega or google, I also wouldn't say no.

Please comment if you find other sites that work the same way.