Tesco F&F are selling these superbly cute Reindeer Pyjamas for £3 or £3.50 depending on size. There's free click & collect and you'll still be able to collect before Christmas eve, but time is running out. It's probably a little late for guaranteed standard delivery, but for £5 you could have next day delivery.
The sizes on this one are a bit limited, with three sizes available for 2-3, 3-4 and 5-6 year olds, and while the description mentions 'him', I could quite happily see my girls prancing around in these.
These aren't pure cotton, but are 'cotton rich' long sleeved pyjamas, presented in a gift ribbon. They have a crew neck for comfortable on and off, and comfortable bottoms with an elasticated waist.
They should be a cute addition to a Christmas eve box!
Thanks to beth25 at HUKD