For those willing to use lead, we have purchased pure-Pb round sinkers in bulk from eBay vendor B&W Tackle to supply our workshops, and can recommend them based on our experiences (search their store for "flat round sinkers"). Their prices were reasonable, the product was well-packed, and shipping is free (a nice bonus when shipping something heavy). When you place your order, state in the "comments to seller" at checkout that you want your sinkers made without eyelets. You might not get an acknowledgement of your special-request comment, but in our experience they always arrived just as requested - without eyelets - and at no extra cost. However, because they are custom made, it may take an extra three (3) days or so to ship out.
There are other sources and vendors on eBay that sell the same or similar product, but the price-per-pound happened to be cheapest with this vendor at the time of our purchase, especially when we factored in the free shipping. (Quantity purchases obtain discounts.) This online tackle shop also makes it easy to order the sinkers sans-eyelets. I have no vested interest in this business, but using an online supplier of easy-to-install lead discs is definitely less hazardous (and likely cheaper) for ordinary derby construction purposes than DIY molten-lead pouring.
For those that still prefer or require tungsten, I have gotten very competitive pricing in the past from a supplier mentioned over in this thread, when they have the shape(s) you want (the availability of some shapes seems limited at times). Again, no vested interest in this business...
