items that add a slot to potion belt:
http://eqitems.13th-floor.org/itemsearch.php?searchtype=advanced&field_0=potionbeltslots&compare_0=%3E&text_0=0&next_0=5&field_1=&compare_1=&text_1=&next_1=0&field_2=&compare_2=&text_2=&next_2=0&field_3=&compare_3=&text_3=&next_3=0&field_4=&compare_4=&text_4=&next_4=0