This TV uses NEC1 protocol device 132.224. Here are three remotes which have a setup code for these Sylvania/Emerson TVs:
RCA RCRP05B ($15 at Walgreens, $20 at Best Buy) This remote has a dedicated Aspect button.
OneForAll URC-8820N or sister 10 device remote URC-10820N (must be N suffix) (<$20 at Sears) Has a Format button which I suspect will shoot an Aspect command. If not, the EFC is 00125. Use the 9XX command instructions
to do a 994 EFC keymove to assign 00125 to the Format button.
These remotes are typically avaialable on-line also.
Use either setup code 1864 or 1886.