Any of the direct indexing providers will let you blacklist individual stocks from the index. The intended use is to exclude stocks you hold elsewhere (or receive as stock grants) to avoid causing wash sales, but it can also be easily used to make a custom "S&P 499".

I'm looking at Schwab (and saw a few others) and couldn't find anything: https://www.schwab.com/learn/story/primer-on-wash-sales

I would assume this is not an ETF but sth else?