Wow, that's a lot of hair!  Maybe if you turn the towel the long way away from you it would be enough.  I'd be concerned that a beach towel would be too heavy.  These microfiber towels are pretty light, and they dry quickly.

Welcome!  Good Luck, let us know if it works!

I use a micro fiber towel that is intended for dog grooming.  It is the size of a bath towel.  I can wrap the length of my hair in the towel when used long-wise.

I also have an XL pack towel which is another type of micro fiber towel that dries VERY fast.  It is great when we are camping.  It soaks up the water from my hair and dries out quickly.  No mildew to worry about.

I purchased my towel at REI.  They have their own brand, but also carry other brands.  Any of the pack towels would probably work just fine.  Campmor also carries pack towels in a variety of sizes.

I bet they would.  Another place to try is a pet store like PetSmart or Pet Warehouse.  They carry towels for dog grooming that work just as well.

Here's a chuckle for you.  When I was looking for a towel in a bigbox pet store, a clerk was trying to help.  They asked what size dog I needed the towel for.  I debated my answer for a second, and said - St.Bernard.  She found the towel - XL size for me and commented on how difficult it is to groom St.Bernard's, due to their size and heavy coat.  I then admitted I didn't have a St.Bernard but wanted the towel for my hair.  The look on her face was priceless.  Total shock.  I took my hair out of its bun and showed her the length.  She then commented that she was not sure the XL was big enough!!! (and then laughed).  I'm sure she's told the story many times of the woman with a St.Bernard hair looking for a towel.

How are you using your towel?  I gauge the size of the towel by the length, not width.  If the towel is about 1 foot longer than my hair, then I know I can wrap my hair in it. 

I start by placing one end of the towel on my head.  Then take the sides of the towel and wrap them around my wet hair starting at the nape.  I continue to wrap my hair with the towel all the way down - I am not twisting my hair at all, at this point, just wrapping the towel around it.  Once I've done that, I start at the far end of the towel and start twisting it gently, like I would do to twist my hair for a bun.  I then wrap this "rope" around my head, like a crown, over the towel that has been just lying there (soaking up water).  I tuck the end of the towel under the start of "crown", then take whatever corners are in my face and tuck them under the rope as well.  This will hold quite well as I dry off, get dressed and do whatever.  When I take the towel off, my hair is damp and at a good point for air drying.