There is a difference between one who undertakes a permissible journey but commits an evil deed whilst travelling, and one who travels expressly for the purpose of committing evil deeds. It is permissible to help the former with his journey, unlike the latter As your work involves making bookings for official delegations whose journeys are for permissible purposes, there is no blame on you for making bookings for them, and whoever commits prohibited deeds whilst travelling, he is the one who will bear the burden of the sin for that in full.

If you cannot interact with these websites except by paying a subscription fee, then it is not permissible for you to deal with them, because that comes under the heading of gambling with one’s money and Riba-based transactions in the contract.