Stumbled upon a very interesting page by Santos Pedraz Marcos with a collection of standard stars, I found this table of blank fields:
Name RA1950 DE1950 Reference Roeser1 00 16 25.0 +16 09 00 CL 0016+16 Cadis1H 01 45 01.3 +02 05 07 Cadis Blank1 04 25 46.0 +54 09 03 PASP 97,363 Cadis9H 09 10 28.0 +46 26 23 Cadis Cadis10H 10 49 00.0 +57 41 52 Cadis, Lockman Hole Cadis10H 10 49 00.0 +57 51 52 Cadis Blank2 12 26 49.8 +02 17 56 PASP 97,363 BlankUH 13 07 47.9 +36 15 08 priv.com. 3 brighter *, else empty HDF 13 34 35.5 +62 29 28 Williams et al 1996 AJ 112,1335 Cadis13H 13 45 11.4 +05 52 32 Cadis Cadis13H 13 45 51.4 +05 52 32 Cadis Cadis16H 16 23 28.9 +55 50 47 Cadis Blank3 16 49 42.0 -15 21 00 PASP 97,363 (? RA:1982,DE:1982) Cadis18H 17 59 43.0 +66 21 20 Cadis (NEP) Blank4 19 19 09.0 +12 22 05 PASP 97,363 Blank5 21 26 54.4 -08 51 41 PASP 97,363 Cadis23H 23 13 16.5 +11 10 09 Cadis Roeser2 23 45 45.0 +00 40 40 priv.com. Blank6 23 54 08.9 +59 28 18 PASP 97,363