может кому полезны будут не только российские системы, вот мой небольшой списочек, составлял когда то для себя:

https://ikajo.com/

https://www.payza.eu/

https://www.mollie.com/en/

https://squareup.com

https://www.paysera.com

https://www.klarna.com

https://www.payolee.com/

https://www.merchantinc.com/

https://www.mondido.com/

https://www.billpay.de

Braintree

https://orange-pay.com/

https://www.ideal.nl

https://www.ariasystems.com

https://www.gopay.com/en/ 

https://www.propaypayments.com

https://www.globalpaymentsinc.com

https://www.sagepay.co.uk/
https://go.wepay.com

Infusionsoft

https://www.mangopay.com/
paytm

https://www.vantiv.com/

https://www.firstdata.com

Heartland

TSYS

https://swipeps.com/

https://www.moneris.com/

https://www.neteller.com

baseratesms

SecurionPay

VirPay

Paycertify

https://www.adyen.com/
https://www.paycron.com/

wirecard

klikandpay

https://www.mypos.eu/
get2pay

click2pay

PxPay

ALTAR

ccnow

paystack

StrictPay

lyra

flutterwave

PSI Gate
paypoint

BancTec

Egopay

PesoPay

Dragon Pay

Smart Money

Jvzoo

Payumoney

Okpay

Solidtrustpay

fondy
https://www.lemonway.com/en/
zilra.co

payproglobal.com

fastspring.com

avangate.com

mycommerce.com

Securetrading.com