Another thought - you could modify an electrical P clip:
https://www.google.co.uk/search?q=electrical+p+clips&biw=1093&bih=479&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiZ8pLz_djMAhXFvRoKHbZFAgEQ_AUIBygC" onclick="window.open(this.href);return false;
Thanks for posting this my fuse holder has been flopping about the engine bay. Strip of scrap stainless steel, bit of drilling, bending and filing and half an hour later had one to fit.