Welcome to the forum and congrations on your new Hunter 19!!
Is yours a 19-1 or 19-2? As long as you provide your sailboat I / J dimensions of 21' / 6.5' or 6.75'
SailboatData.com - HUNTER 19-1 Sailboat or
SailboatData.com - HUNTER 19-2 Sailboat, material (dacron, laminate, etc.), weight depending on wind conditions (e.g., 4 oz Dacron is suitable for light air), and size from 90 - 155% (amount of overlap or luff perpendicular [LP]), sunshield (consider Sunbrella) and requirement for a luff flattener (makes a partialled furled sail flatter in the middle. Stock headsail is likely Dacron and 100% size. If you like your current headsail sail size.........measuring the sail luff (leading edge of your sail), leech (trailing edge of your sail) and the foot. These measurements will be used to compare the measurements that you take from your rig to ensure that everything is working out well. It will also give your designer an idea of what the current sail size is.
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For example, this site sells a 4 oz. Dacron sunshield, luff flattener and a couple of options in 100% - 150% one:
Sail Loft (hunterowners.com)