Yes, you can make a one-time purchase instead of buying a subscription.
For this, you can buy Scanova's Ultra-Lite plan. It allows you purchase a single Dynamic QR Code, which will work for a lifetime. Some of the features of this plan are:
Mobile landing pages
QR Code designing capabilities
Raster and vector export
Basic analytics (number of scans by time period)
For more details, refer to Scanova's pricing.