First off, you'll bash your head against the wall trying to find cut-to-fit chains for non-OEM sprocket sizes. Learning to cut chains to fit is much easier than trying to figure what link count fits what sprocket combination. A file will do the job. A Dremel makes it easier. A chain breaker tool easier still. Any will be cheaper in the long run than one error in sizing OR paying someone to cut a chain for you every time you need one, both likely outcomes in a search for non-OEM products.
Second, 428 chains fit TW sprockets. Any other size will not fit properly. The 428 designation has nothing to do with how many pins (links) a specific length of chain has. The 428 designation specs the distance between the pin centers, the outside diameter of the rollers, and the inside distance between the plates. Nothing more. Therefore, a size 428 chain is the first thing you must know when ordering a chain.
Third, the second criteria for selecting a chain is tensile strength. The EK 428 SROZ chains I use have a tensile strength of 5300 pounds and cost $55-60. RK's 428SO o-ring chain has a tensile strength of 5500 pounds and cost $65-70. DID Pro V o-ring chains have a tensile strength of 5340 pounds and run $75-80. Any will get the job done.
As far as open chains, I have seen cheap off-brand 428 chains with tensile strengths of 3200 pounds at costs under $10. Parts Unlimited's store brand economy chain has a 4000 pound tensile strength and costs $12-15. the OEM chain seems to be somewhere between these first two. DID Standard Roller Chain has a tensile strength of 4280 pounds and costs $20-25. DID NZ High Performance 428 has a tensile strength of 5740 pounds and is an open chain for those into ultra high performance and costs $50-55, but for just $5 more I can get an EK SROZ 428 with o-rings and cut chain maintenance by 90% and double or triple chain life. It's a no-brainer--the best value for a chain for most people (low maintenance, long life) is obvious.
Fourth, to find a bazillion sources for any particular chain use Google. For instance, type in "SROZ 428" without the quotation marks and the first 10 hits will be online retailers of SROZ 428 chains.