Who doesn't love cute cuddly plushies?! Even if those cute and cuddly things are pretty sinister in game... Amazon seller JOY IS TOYS offers two super adorable Undertale plushes -- Sans and Toriel. The toys are priced separately with Sans costing $27.99 and Toriel running $24.98.
Unfortunately, these two items are not eligible for Amazon Prime, so you will have to drop $5 on shipping as well. But as plushies go, it's still not a bad price.