Products from the Christmas display were placed into a handbag and taken from the store.
Police said: “We are eager to hear information about a woman described as slim, mid 40s, dark hair to her shoulders, wearing glasses, a skinny green top, grey cardigan, light coloured skinny ripped jeans, white trainers, and carrying a large white leather handbag.
“We are also keen to hear about a man described as white, bigger build, 40s, carrying a walking stick, and wearing a flat cap, black jacket with light t-shirt and dark jeans with red trainers.
“If you can help with this enquiry, or can recognise the people in the picture, please get in touch.”
Contact Lincolnshire Police by calling 101 and quoting incident number 337 of October 4, or email [email protected]
Alternatively, call Crimestoppers anonymously on 0800 555111.