OLFA 18mm Heavy-Duty Utility Knife (L-1) - Multi-Purpose Custom Cutting Depth Utility Knife w/Ergonomic Grip Handle & Snap-Off Blade, Replacement Blades: Any OLFA 18mm Blade

For the price, quality and ergonomics you can't do better that Olfa IMO... https://www.amazon.com/Olfa-Craft-Kife-size-34B/dp/B000TGF9DI https://www.amazon.com/OLFA-Cushion-Grip-Art-Knife/dp/B0006O87TQ https://www.amazon.com/5003-Ratchet-Lock-Heavy-Duty-Utility-Knife/dp/B0006SJAR0 ..those are all tried and true, and yes, plenty more expensive things to cut with, but why try to reinvent the wheel!? Also, it's so easy to touch up any "disposable" blade with a sharpening stone, get on and learn to use it. Olfa steel is well known for their quality too. Get a large rotary cutter for thin stretchy leather...