I'll try to find some sandal makers. If it's womens sandals I have a lot of options, but mens are harder to find. I guess you're right about the sand part. I found these on amazon. Emma Shoes DKR BIO | Men's Eco Sustainable Two Straps Slide Sandals in Recycled Material - Made in Spain https://www.amazon.ca/dp/B08DCL4L9V/ref=cm_sw_r_cp_tai_TIGhFbC294H20

Would this be better?

Try searching mens sandals made in spain on amazon.

Or this

https://www.amazon.com/Pikolinos-Tarifa-Slide-Sandal-Cuero/dp/B01594RV4O/ref=sr_1_13?dchild=1&keywords=Made%2Bin%2BSpain&qid=1595804010&s=apparel&sr=1-13&th=1

or these

https://thespanishsandalco.com