How little?
I've just bought two fantastic,secure ,made to measure leather harnesses for my mini schnauzer..cost.33 pounds each in attractive leather and brass,and I doubt any dog would wriggle out as they have a lovely padded frontpiece and buckle straps which can be adjusted to size...they should last years too. http://mbdogharnesses.co.uk/Studded-dog-harness-37-01-05
Prior to this we used the trixie harnesses but I found they ride forward behind the elbow and I would doubt they would be escape proof.
there is a harness called a houdini harness, I cant remember the company but if you google it it will come up. it has an extra strap under the belly. To be honest though a well fitted collar is the safest option, at the vets we see dogs that have slipped harnesses owners thought were ok far too often and sometimes the results are not pretty.
Find/ make a strap with clips both ends to connect the collar to the harness. If they back out of the harness they cannot get loose. The only harnesses a dog cannot back out of have an extra strap which fastens just behind the last ribs.