There is no universally accepted physical object that can be demonstrated scientifically to have belonged personally to Gautama Buddha.
For example, Buddhist traditions preserve relics of the Buddha, including purported bone and tooth relics.
But scientifically establishing:
โThis particular bone definitely belonged to Gautama Buddhaโ
is extremely difficult because there is no authenticated DNA reference sample from the Buddha and the relic traditions developed within ancient Buddhist communities.
So relics are religious/historical evidence, but they aren't equivalent to modern forensic identification.