You can use your own HTTPS certificate on RUT240, as RUT240 uses self-signed certificates: https://en.wikipedia.org/wiki/Self-signed_certificate
To use your own HTTPS certificates on RUT240 go to System -> Root CA. But if you want to make connection from RUT240 to webcame to be in HTTPS then you can try using Stunnel feature, under Services -> VPN -> Stunnel and simply enable it, add new Stunnel configuration also enable it and enter:
Operation mode: server
Listen IP: 0.0.0.0
Listen port: port number which will be used for making connection to end device, example 6000
Connect IP's: IP + port number to which connection will be redirected, for example 192.168.1.244:5000
Upload certificates: you can use X.509 certificates.
After that even thou end device only supports HTTP, you will be making HTTPs connection to that device.