There was a wood water tank located at Longfellow, PA that served two standpipes located between the nos. 1&2 and 3&4 tracks. The stone foundation still exists but, the wood part collapsed years ago.
For photos of wood PRR water tanks; I would recommend a book put out by the PRRT&HS back in 2000 titled "Lewistown and the Pennsylvania Railroad". This book has numerous photos of PRR water tanks in central PA including the twin tanks at Denholm, PA as well as a couple on the Sunbury & Lewistown branch.
I've no idea if this book is still available but, if interested, a place to start would be to reach out to the PRRT&HS. I think the Mifflin County Pennsylvania historical society also sold these books when first published so they might be a plan B if you strike out with PRRT&HS.
Curt