Bloomberg terminal is probably the best single source, but most of us don't have access to that. Next would be going to the source, for example the Blackrock ETF (IBIT): https://www.ishares.com/us/products/333011/ishares-bitcoin-trust
Or, for simplicity, follow @EricBalchunas or @JSeyff on Twitter. They're the Bloomberg ETF analysts and they've been posting what you're asking about. Specifically, here's how they all closed out Friday:
Looks like the ETFs have been added to https://bitcointreasuries.net so that might be a good place to get data
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