Do you have a friend with a Mac? If you do see if they can create an OS installer drive following this guide: [https://www.macworld.com/article/3204672/macs/how-to-create-a-bootable-macos-high-sierra-installer-drive.html|How to create a bootable macOS High Sierra installer drive]. You'll still need access to a USB keyboard so you can tell the system to boot to the USB installer drive holding the Option key.
Reference: [https://support.apple.com/en-us/HT201255|Mac startup key combinations]