hi linda, welcome to the forum
i'm so sorry to hear you lost your vanillus
i have nothing much more to add that hasn't already been suggested.
a safe enclosure similar to kim's seems the best bet in my opinion.
they are inquisitve creatures by nature & will be interested in windows & doors, you just have to be strong & strict with yourself & not succumb to them
if you decide to try a lead & harness it needs to be a regular excursion or else they will be demanding out all the time.
i feel access to a safe enclosure so they can come & go as they please, getting fresh air & insects to chase & birds to watch, but no risk of the dangers of outdoors is the best option really.
also make sure you have lots indoors to keep them occupied, things to climb & scratch & play with & plenty of one-on-one time playing with them as they really do thrive on interaction.
i really hope it doesn't put you off getting another, as they are such wonderful companions