How to change "OK" word button in contact vendor page

-- HikaShop version -- : 4.0.1
-- HikaMarket version -- : 3.0.0
-- Joomla version -- : 3.9.1
-- PHP version -- : 7.0.2
-- Browser(s) name and version -- : CHROME
-- Error-message(debug-mod must be tuned on) -- : Replace OK button

Hello,

In contact vendor page for a product (see Url), I just would like to rename "OK" by "Send"
I already tried to override: HIKA_OK="Send"

Code:

<div class="toolbar" id="toolbar" style="float: right;">
			<button class="btn" type="button" onclick="checkFields();"><img src="/media/com_hikashop/images/ok.png" alt="">OK</button>
			<button class="btn" type="button" onclick="history.back();"><img src="/media/com_hikashop/images/cancel.png" alt="">Cancel</button>
		</div>