I didn't find an article for service innovation in the banking industry. I think that you will find the following article interesting:
Taghizadeh, S. K., Jayaraman, K. S., & Ismail, I. (2019). Innovation value chain as predictors for innovation strategy in Malaysian telecommunication industry. Management, 12, 4-2.
To be honest with You according to "Oslo Manual 2018 Guidelines for collecting, reporting and using data of innovation", there aren't service innovations. There are in business innovations. In the earlier edition of this guidelines there weren't service innovations too. There were in product innovations. I don't know a special questionnaire for measuring service innovation but I suggested You reading "Oslo Manual 2018 Guideliness for collecting, reporting and using data of innovation" or the 3rd edition of it from 2005 (both are available in the Internet in the pdf files). There are everything connected with innovativeness and this is the core of knowledge about innovativeness and innovation in OECD countries but not only I think
. Moreover I suggested You create Your own questionnaire, where you explore not only service innovations but more. Whatever, the questionnaire is determined would You explore exactly.
I THINK IT COULD BE UNIVERSAL QUESTIONNAIRE ABOUT INNOVATIVE ACTIVITIES WITH QUETSIONS ABOUT: SCALE OF NOVELITY THIS INNOVATION (IN EXAMPLE: NATIONAL INNOVATION, REGIONAL INNOVATION ETC.), SOURCE OF INNOVATIVE IDEAS (INTERNAL AND EXTERNAL TOO), SPECIFIC KIND OF SERVICE INNOVATION (IN EXAMPLE: INNOVATION DEBET CARD), EFFECTS WHICH ARE GENERATED BY INNOVATION (IN EXAMPLE REVENUE FROM SELLING INNOVATIVE SERVICES).