Are there any available block explorers that will supply a transaction's wtxid
and its corresponding merkle proof of the said wtxid
?
If not, how would I retrieve this if i'm running bitcoind?
There is the gettxoutproof RPC that retrieves merkle proof in Bitcoin Knots.
There is the public server which can be used for the gettxoutproof RPC: https://bitcoinexplorer.org/rpc-terminal.
The gettxoutproof RPC result could also be obtained from: https://blockstream.info/api/tx/86639c0c9bdb83f467f2c07910367929171196c8907743a5915d555de5bc27eb/merkleblock-proof (replace 86639c0c9bdb83f467f2c07910367929171196c8907743a5915d555de5bc27eb with your txid in the URL).
More info at https://bitcointalk.org/index.php?topic=5335699.msg64441291