There are many schools and institutional programs that offer a Diploma RN or Associate Degree Nurse (ADN) to Master's Degree in Nursing (MSN) degree directly, without adding additional courses for the Bachelor's Degree in Nursing (BSN). One could also look specifically for the program term of RN to MSN.

Many schools offer programs where the nurse receives a congruent BSN along with the MSN by the end of the program. These programs are ideal for the nurse who completed an ADN program, obtained a bachelor's degree in a field other than nursing, but would like to complete a MSN degree.

Here is a breakdown of RN to MSN programs by state:
https://www.registerednursing.org/rn-to-msn/#find-rn-msn-programs-state

Students should always assure that the intended school offering a direct ADN to MSN program is accredited by at least one of the national nursing school accreditation bodies. Attending institutions that have been accredited allows students to apply for federal student loans and state entitlement programs. The accreditation process for schools is also a guarantee of professional and academic standards. Graduates from accredited programs are most likely to qualify to attend other accredited schools for advancing degrees. Most employers prefer, if not require, nurses to have received their degree from accredited programs.

There are two national organizations that accredit nursing education programs. The Accreditation Commission for Education in Nursing (ACEN) accredits all types of nursing programs including diploma, associate's, baccalaureate, and master's. The Commission on Collegiate Nursing Education (CCNE) accredits programs that offer only baccalaureate and master's level nursing degrees.