If you cannot afford human hair wigs, try considering FUTURA fiber with 180% density or more 30-40 inches on Alibaba (customizable from 2/5/10 MOQ depending of the supplier) if you can convince her to wear wigs sometimes. Classic length (30" to 40", depending of her size) is the best manageable/pleasurable/best looking and feeling during love (you can feel the hair almost everywhere on your upper body) IMHO. Tested and approved for years.
My wife is wearing wigs everyday and the best days was when she was wearing a 200% density Mongolian human hair classic length wig (34 inches long bob after professionally cut, no fucking layers). We cannot found this today anymore at the price we got it 7 years ago, three times in a row every 1.5 years for +/- only 1000 USD). She currently has Brazilian virgin 27" 150% and we are going to buy the same quality but 30" 180% very soon.
She has Alopecia totalis (no hair at all) and she knows about my love for long hair. That's weird ikr. When I meet her for the first time, she was wearing ultra short plastic wig (middle of 200s), so I never thought at the beginning she could "fulfill" my love for long hair until years after we were together so "NO", I didn't choose her for her condition but in another way she already used to wigs so "YES", she accept to wear super long wig for me sometimes, as long as they have high quality caps and features to avoid skin itches. I cannot complain.
After all, high quality synthetic wigs that can able to "fulfill" people like us are so rare and expensive today so imagine the bad technology 20 years ago.
alibaba.com/product-detail/BeautyTown-Bone-Straight-Brown-Best-Futura_1600494549355.html
alibaba.com/product-detail/30-Inches-430-Silky-Lace-Front_1600427645916.html
Sometimes supplier can accept to customize FUTURA until 40 inches. You can find customized 50 inches from here too: georginathedollwigs.com/
You can find longer than 50 inches but personally, it's hardly manageable when longer than 120 cm / 47 inches.
Try your luck.
FUTURA fibers is the best you can find today until ULTIMA (almost synthetized human hair) is invading the market someday...