\xe3\xff\xe3\xcd\x03\x800\xf9v
Note that non-ascii characters in the above source code will be escaped (such as \x9f).
Disassemble:
ORG 00000H EX (SP),HL ;0000 E3 . RST 38H ;0001 FF . EX (SP),HL ;0002 E3 . CALL 08003H ;0003 CD 03 80 . . . JR NC,$-5 ;0006 30 F9 0 . HALT ;0008 76 V