Yea I've been using Pentel and it doesn't give me any problems

http://www.amazon.com/Pentel-Hi-Polymer-Refill-Pieces-C505-2B/dp/B004AMH3UE/ref=sr_1_4?ie=UTF8&qid=1445982440&sr=8-4&keywords=0.5+lead

but There is a cheaper option at ebay

http://www.ebay.com/itm/Refill-Lead-Mechanical-Pencil-160-Spare-Lead-HB-Bazic-0-5-MM-/221917726992?hash=item33ab53c910:g:W1IAAOSwsB9V~Qea