You could use OA automation stored procedures with the Scripting.FileSystemObject

EXEC @ProcRC = sp_OACreate

 'Scripting.FileSystemObject',

 @fso output

-- create File Object

EXEC @ProcRC = sp_OAMethod

 @fso,

 'GetFile',

 @fso_file output,

 @FULL_FILE_NAME

-- Get File Size

EXEC @ProcRC = sp_OAGetProperty

 @fso_file,

 'Size',

 @fso_file_size output