Need the path for particular files using os.walk()

os.walk gives you the path to the directory as the first value in the loop, just use os.path.join() to create full filename:

shpfiles = []
for dirpath, subdirs, files in os.walk(path):
    for x in files:
        if x.endswith(".shp"):
            shpfiles.append(os.path.join(dirpath, x))

I renamed path in the loop to dirpath to not conflict with the path variable you already were passing to os.walk().

Note that you do not need to test if the result of .endswith() == True; if already does that for you, the == True part is entirely redundant.

You can use .extend() and a generator expression to make the above code a little more compact:

shpfiles = []
for dirpath, subdirs, files in os.walk(path):
    shpfiles.extend(os.path.join(dirpath, x) for x in files if x.endswith(".shp"))

or even as one list comprehension:

shpfiles = [os.path.join(d, x)
            for d, dirs, files in os.walk(path)
            for x in files if x.endswith(".shp")]