Try a looking at sawmills. If youre looking at western cedar 23400 I-35, Kyle, TX 78640. Jane Holand (sawmill 1 hour away) 5129233688, may be able to do cedar or mezquite for you.
I just recently came into some cedar beam pieces 4"x16". I know it’s not exactly what you’re looking for, but could be a workaround. I have one that is 8’ long and the rest (6-7 pcs) are varying shorter lengths from 57.5" down to about 30".
General condition is decent; the pieces were reclaimed from a house in Point Venture. There is some insect damage on some of the pieces. The 8’ beam is in the best condition, the smaller pieces have more of the insect damage, but dependent on your finished size could be milled down. I typically stay around $10/bd ft for all of my lumber (I also mill slabs from larger trunks w/a chainsaw mill). If you want to text me your #, I can see about sending you some pics this afternoon. (512)731-9728